WEC Projects sewage treatment vs septic tanks

The differences between sewage treatment plants and septic tanks are not as obvious as one might think because, in fact, they both dispose of waste responsibly. Sewage treatment plants are WEC Projects’ business, but if there is uncertainty as to what this means, the following information should aid in distinguishing the two systems in question. One should consider the following before investing in a waste removal system.

What is a sewage treatment plant?

A sewage treatment plant is a system that treats sewage with conventional activated sludge systems, biological trickle filtration, submerged membrane bio-reactors, and even Nereda® which uses the unique features of aerobic granular biomass. WEC Projects designs easily transportable, packaged sewage treatment plants that can be installed anywhere in Africa or can simply add value to existing treatment plants.

What is a septic tank?

A septic tank is an underground, watertight chamber that acts as an onsite sewage facility; it separates solids from liquids after time. A biological process occurs in a septic tank that partially treats the sewage in anaerobic conditions.


A sewage treatment plant requires electricity to run because it is an active system with rotating discs that initiate the aerobic bacterial digestion of sewage. While all plants introduce air into the process, they do not do so in the same way. This forced aeration allows water treatment to occur in much less time than it might take a septic tank. The amount of electricity the system requires depends on the set-up and size of the machine.

It is useful to note that Nereda®, the advanced biological wastewater treatment technology, actually saves up to 50% in energy consumption while still producing excellent effluent quality.

A septic tank does not require electricity because it makes use of a self-forming bacteria to which the term septic refers – this is the anaerobic bacterial environment that the tank creates.


Sewage treatment plants can only be installed if one has the relevant permit. Once the permit has been received, the plant will need to be serviced regularly. The sewage plant should be emptied every three to sixty months, depending on the size and type of sewage treatment plant that it is. Customised plants are ideal because they can be optimised for specific applications – which makes maintenance more convenient too!

Septic tanks can last underground for as long as fifty years if they are well installed. However, they do need to be emptied at least once a year (depending on the tank you are using) to avoid the spread of contaminants.

Polluting effect

Sewage treatment plants in South Africa treat water in compliance with general and (stricter) special limit values. This ensures the water is considered to be non-polluting; it can be discharged into a watercourse once it has been approved by an environmental agency.

Septic tanks can only produce a substance that still contains a large amount of the polluted matter.  This means that it will need to go to a treatment facility before it can be discharged.

Sewage treatment plants are more effective when it comes to treating waste even though certain situations may be better suited for a septic tank. Sewage treatment plants are the preferred option for sustainable waste treatment. Consult WEC Projects for services that are focused on the specific needs of every customer.

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